Streaming Digital Content Synchronization

1. In a digital medium environment to stream digital content, a method implemented by a computing device, the method comprising: receiving, by a computing device, a response to a request to stream the digital content, the response including a time at which the digital content was last modified and a time at which the response was generated; calculating, by the computing device, an age by subtracting the time at which the digital content was last modified from the time at which the response was generated; determining, by the computing device, a time by subtracting the age from a predefined set-back time, the time usable to define when rendering of the stream of digital content is to occur; and rendering, by the computing device, the stream of the digital content based at least in part on the determined time.

2. The method as described in claim 1 , wherein the time at which the digital content was last modified is set using a clock of the content distribution service that originated the response as part of a last-modified header.

3. The method as described in claim 1 , wherein the time at which the response was generated is set using a clock of the content distribution service that originated the response as part of a date header.

4. The method as described in claim 1 , wherein: the response further includes an age header indicative of an amount of time the response has spent in at least one cache; and the calculating of the age includes adding the age header.

5. The method as described in claim 4 , wherein the cache is included as part of a content distribution service that streams the digital content or an intermediary between the content distribution service and the computing device, via which the response is communicated.

6. The method as described in claim 1 , wherein the response includes a manifest file mapping time periods to respective segments of a plurality of segments within a media presentation of the digital content.

7. The method as described in claim 1 , wherein the request, the response, and the rendering are configured in accordance with a hypertext transfer protocol.

8. The method as described in claim 1 , wherein the last-modified header or the date header specify fractional parts of a second.

9. The method as described in claim 1 , further comprising ascertaining, by the computing device, an amount of time between revisions to the digital content, and setting the set-back time based at least in part on the ascertained amount of time.

10. The method as described in claim 9 , wherein the ascertaining is based on respective amounts of time at which respective segments are added to a media presentation of the digital content.

11. In a digital medium environment to stream digital content, a method implemented by a computing device, the method comprising: communicating, by the computing device, a hypertext transfer protocol (HTTP) request for a manifest file to stream the digital content; receiving, by the computing device, an HTTP response to the request, the response including a last-modified header, a date header, and the manifest file; calculating, by the computing device, an age by subtracting the last-modified header from the date header; determining, by the computing device, a time by subtracting the age from a predefined set-back time, the time usable to define when rendering of the stream of digital content is to occur; obtaining, by the computing device, at least one segment of the digital content from a media presentation based on the manifest file and the determined time according to the hypertext transfer protocol; and rendering, by the computing device, the at least one segment of the digital content based at least in part on the determined time.

12. The method as described in claim 11 , wherein: the last-modified header is set by a content distribution service that originated the response, the last-modified header indicating a time at which the digital content was last modified as indicated by a clock of the content distribution service; and the date header is set by the content distribution service that originated the response, the date header indicating a time at which the response is generated as indicated by a clock of the content distribution service.

13. The method as described in claim 11 , wherein: the response further includes an age header indicative of an amount of time the response has spent in at least one cache; and the calculating of the age includes adding the age header.

14. The method as described in claim 11 , wherein the last-modified header or the date header specify fractional parts of a second.

15. The method as described in claim 11 , further comprising: ascertaining, by the computing device, an amount of time between revisions to the digital content; and setting, by the computing device, the predefined set-back time based at least in part on the ascertained amount of time.

16. The method as described in claim 11 , further comprising checking, by the computing device, logical consistency of the last-modified header with respect to the date header and wherein the calculating, the determining, and the rendering are not performed responsive to the checking that the last-modified and date headers are not logically consistent.

17. In a digital medium environment to stream digital content, a system comprising a playback module implemented at least partially in hardware of a client device, the playback module configured to perform operations comprising: ascertaining an amount of time between revisions of the digital content; calculating an age as a difference between a last-modified header and a date header in a response to a request to stream the digital content; determining a time by subtracting the age from a set-back time, the set-back time based at least in part of the ascertained amount of time between the revisions, the time usable to define when rendering of the stream of digital content is to occur; and rendering the stream of the digital content based at least in part on the determined time.

18. The system as described in claim 17 , wherein: the last-modified header is set by a content distribution service that originated the response, the last-modified header indicating a time at which the digital content was last modified as indicated by a clock of the content distribution service; and the date header is set by a content distribution service that originated the response, the date header indicating a time at which the response is generated as indicated by a clock of the content distribution service.

19. The system as described in claim 17 , wherein: the response further includes an age header indicative of an amount of time the response has spent in at least one cache; and the calculating of the age includes adding the age header.

20. The system as described in claim 17 , wherein the last-modified header or the date header define fractional parts of a second.